So my window on my 38k mile 2002 Pontiac Grand Prix Gt still works fine one day and then the next day nothing, it wont go down....... How much would a dealer charge to fix this window????

Window regulators can be purchased from Ebay from 70-150 Not too hard of a DIY. Not sure what a dealer will charge. Iirc they want atleast 200 for the parts alone and probably 2 hours of labor.

the motor and regulator is only like $125 or so and its really not hard at all to do

Won't go down sounds like the switch.... Make sure the motor has power going to it before changing it. If you know anyone with a GP similar to yours (2 door/4 door) you can easily swap switch boards.
Not sure how much a new switch goes for, but I believe ZZP is selling them used and would be an easy fix for yourself to do.

Yes I second crimpton... I would try switch first. Simple things first

Regulator at the dealer installed in an 02 Bonneville was $460 for a family member

Wow, somedays it works fine and when it works it works with both switches on the passenger side and the drivers side. Then somedays its in the up position and it doesnt move at all!!!!!!!!!!

Its really weird... Whats wrong with this window???????????

Its really weird, somedays it works and some days it doesnt. When in the up position it doesnt go down when either the driver or passenger side switches are used. Then somdays it works fine. Whats the deal with this????

Sounds like a switch is going out... If I remember correctly, there's something about the wiring that could make it where if one switch goes out it can make it where the other switch associated with the window won't work either.

So, if one of the switches is being a pita, that could be your issue.